Propeller hub



PRQPELL R nus Filed Nov. 19, 1931 5 Sheets-Sheet 1 V IN VENTOR.

A ORNE Y.

W. S. HOOVER .PROPELLER HUB u 9 l 4 .L D. hm

Filed Nov. 19. 19s; 5 Sheets-Sheet 2 l1 INVENTOR.

A T? ORNE Y.

Sept. 4,. 1934.,

W. S. HOOVER .PROPELLBR HUB Filed Nov. 19, 1931 ao 1 q ll i k .1 I I I v.l l 17 I l "ll I 30 I.

5 Sheets-Shet s A TTORNEY.

Sept. 4, 1934. 1

w. s. HOOVER 1,972,485

I PROPEL LLLL us Filed Nov 19, 1931 5 Sheets-sheaf 4 A YTORNE Y.

INVENIOR. v

Patented Sept. 4, 1934.

PATENT OFFICE- raorELLEa HUB Walter S. Hoover, Girard, Pa, assignor of onehalf to Patrick H. Crow, Meadvllle, Pa.

Application November 19,1931, Serial No. 576,063 11 Claims. (01. 170-173) This invention relates to improvements in hub structures for aeroplane propellers more especially for variable pitch propellers and it is among the objects thereof to provide a hub of durable mechanical construction embodying a minimum number of parts and which is designed to facilitate the machining of the hub castings, and the assembly of the pitch adjusting mechanismwithin the hub casting.

A further object of the invention is the provision of novel means of anchoring the propeller ing the blades rigidly to their adjusted position with perfect coordination of pitch between the blades.

A further object of the invention is the'provision of a reversible pitch propeller hub structure 26 which shall embody sufiicient space for receiving the pitch adjusting and actuating mechanism and which in addition shall provide space for the routing of air or scavenged fumes through the hub and blades.

A further object of the invention is the provision of blade pitch coordinating mechanism which shall be positive in its action, capable of withstanding the imposed thrust, which shall function to normally bias the blades to their extreme forward position of pitch setting if the pitch adjusting actuating mechanism should fail,

and which shall be adapted to automatically stream-line the blades if the motor stops in fiight.

A still further object of the invention is the provision of a hub structure and blade anchorage means therefor of such character as to make possible the employment of hollow metal propeller blades the wall section of which is of relatively thin gage which shall effectively-resist the stresses induced by the terrific thrust loads to which variable pitch propellers are subjected.

These and other objects of the invention will become more apparent from a consideration of the accompanying drawings constituting a part hereof in which like reference characters designate like parts and in which:

Figure 1 is a cross-sectional view of an assemr bled propeller hub structure embodying the principles of this invention;

Figure 2 a sectional elevational view taken through the joint of the two half castings of which. the hub is formed, Figure 2 showing the casting which constitutes the front half of the hub;

Figure 3 a similar view showing the rear half of the hub.

Figure 4 is a side elevational view of a conduit structure for routing the waste gases from a motor through the hub to a pair of vented hollow propeller blades;

Figure 5 a bottom plan view thereof; and, Figure 6 a longitudinal sectional elevational view of the hub and propeller assembly.

With reference to the several figures of the drawings, the structure therein illustrated comprises a pair of castings 1 and 2 having their abutting faces la and 2a, Figures 2 and 3, machined to. an accurate fit. These castings are made of high grade cast or drop-forged steel to give the necessary strength and factors of safety to withstand the high centrifugal thrust loads.

The two castings of which the hub is constituted are clamped securely together by a plurality of clamping bolts 3 which distribute the drive load over the castings as a whole.

The castings land 2 are provided with web portions 4 dividing the ends of the hub into chambers in which are mounted single acting thrust bearings 5 and a pair of split bevelled annuli 6. The members 6 as shown in Figure 1 have sleeve 35 portions 7 which are disposed within the cylindrical portions of the hub projections 8 and have their shoulders 9 abutting against the races 5a of bearings 5. The members-6 are constituted of two halves which are adapted to envelope the root or shank 10 of thepropeller blades (not shown).

The blade roots are provided with anchorage abutments 11 and 11a which fit into comple mentary shaped grooves of the split-members 6 forming a snug fit therewith to securely hold the blades in the hub. The innermost abutment 12- of members 6 prevents the metal at the end of the blade roots 10 from straightening and together with the abutments 13 and 14 prevents the anchorage abutments from stretching in response I to centrifugaltlirust thus permitting use of lighter gage metal in the blade roots.

The races 5a of the thrust bearings have a press fit on the beveled annulus at 15 to rotate therewith and have a radial clearance at 16. The races 5b are loosely fitted in their spaces in the hub, ample clearance being provided at 17 and 18 to render these races self aligning with races 5a through the balls 5. The grooves of the races are very deep to prevent the balls from playing back and forth across the raceways in the direction in which power is applied from the propeller hub thereby eliminating wear and the deep grooves further cause self-alinement of race 5b with 5a. Race 5b does not rotate with member 6 for pitch adjustment.

The ends of the beveled annuli 6 are provided with slots 19 to constitute them spring collets or clamping sleeves which as shown in Figures 1 and 3 are also tapered at their ends 20, the taper terminating into the screw threaded portion 21 which has anabrupt shoulder 22.

A clamping ring or annulus 23 having a screw thread portion adapted to coact with the thread 21 of the member 6 is provided with a taper seating face which intimately contacts with the tapered surface 20 of member 6 to compress the ends of its sleeve 7 as the annuli or clamping rings 23 are drawn on their thread, the ends of the sleeves '7 will contract on account of their spring slots 19 to intimately engage the blade roots 10 thereby firmly locking them to the beveled members 6. Clamping rings 23 areprovided with notches 23a at their ends to receive a spanner wrench for adjustment. Ring nuts 24 are provided to interact with threads 25 formed on the extension 8 of the hub to hold the half sections or castings against separation in addition to the clamping action of the studs 3.

The hub casting 2 is provided with an integrally formed spline member 26 by means of which the hub is mounted on the end of the propeller shaft (not shown).

The castings are provided with grooves 27 and 28 for routing either air or scavenged fumes from or into the hollow propeller blades through conduits, shown in Figures 4, 5 and 6, which are placed in said grooves and establish communication of the hollow interior of the propellers with the engine. I

The beveled faces 29 of the member 6 in which the blade roots are mounted, are provided with deep involute gear teeth 30 around one half of their periphery which interact or mesh with the teeth 31 of a bevel gear 32, Figure 1, which is hereinafter referred to as the pitch-coordinating gear. The gear 32 is normally biased by a torsion coil spring 33' which is secured to the hub of gear 32 at one end and tea hydraulic actuating unit generally designated at 34 at its other end. The spring 33 serves two purposes: It maintains tension of the involute bevel gear teeth in mesh even when elasticity takes place in the hub thus maintaining accuracy of pitch alignment in service and the spring also automatically returns the blades to their extreme .forward position of pitch setting when the motor is stopped. This is also a safety factor in the event of failure of the actuating system as the blades are automatically forced to extreme forward position of pitch setting.

The function of the hydraulic unit 34 is to actuate the pitch coordinating gear 32 to vary the pitch of the propeller blade through hydraulic pressure and control means which is not herein illustrated and which constitutes the subject matter of a copending application serially numbered 578,513, filed December 2, 1931.

However, regardless of the type of actuatingmedium employed, the pitch coordinating gear 32 A with its ten-don spring setting provides a positive and reliable means of controlling the pitch of the propeller blade for either positive or negative setting.

"and exhaust router. The members 36 and 3''! are inserted in the hub castings 1 and 2 and are clamped securely by bolts 41. The conduits 39 fit into the recesses 27 and 28 Figure 3 with the funnel ends 40 disposed in the hollow blade roots 10 of the blades as shown in Figure 6 of the drawings. The semi-annular end chambers 38 are reenforced by radial ribs 42 which also have the function of vanes or blades when revolving with the hub to increase propulsion efiiciency by directing the fumes of the motor exhaust in the direction of propeller rotation.

Some of the outstanding features of the above described propeller hub are the split annuli which firmly clamp the root of the blades and coact with the anchorage abutments, and which enable the standardization of hub and blade design for a variety of motors.

The screw threaded hub rings will-maintain accuracy of hub alignment in addition to the clamping studs.

The removal of the hydraulic unit provides access to the propeller shaft and inner parts of the hub.

The tapered lock ring provides for the adjustment of propeller blade pitch on the ground without disturbing other units and locks the blade rigidly in its adjusted position in the split annulus.

Assembly of the hub is as follows:

The casting ring 24 and the tapered lock ring 23 are slipped on the blade root 10 and then the bearing races 5a and 5b. The split annulus 6 is fitted on the blade root anchorage abutments 11 and 11a and the race 5a is pressed to seat against the shoulder 9 of the member 6. The tapered lock ring 23 is then screwed part way on thread 21 and the ring nuts 24 are securely drawn. The members 23 are screwed fully in place when the ground adjustment is made.

The present design of hub structure eliminates any mechanical leverage, couplings or collars that would cause excessive drag on the motor and power output. It also eliminates wearing parts.

The involute bevel gearing under spring tension in mesh will maintain accuracy ,of pitch alinement regardless of elongation of the hub resulting from terrific centrifugal force due to rapid rotation. With the durability and positive action of the hub structure herein disclosed, the difiiculties heretofore encountered in variable pitch propeller hubs are largely eliminated with the assurance that if the actuating mechanism for varying the pitch is for any reason rendered defective or inoperative, the blades will be auto-. matically set to their advanced position.

Although one embodiment of the' invention has been herein illustrated and described, it will be obvious to those skilled in the art that various modifications may be made in the details of construction without departing from the principles herein set forth.

I claim:

1. A propeller hub structure comprising a pair of half sections having a spline connection for the propeller shaft formed integrally with the rear half section, said sections being joined by a plurality of studs and ring nuts, a plurality of split annuli disposed in the hollow axis of the hub simultaneously adapt them to angular movement.

2. A propeller hub structure embodying a plurality of split annuli for intimately engaging the blade roots of the propeller blade, a plurality of tapered lock rings for intimately engaging a tapered surface of the annuli to securely lockthe blade roots therein, said annuli having gear teeth on their bevel faces, and a pitch coordinating gear having teeth coacting with the teeth of the annuli whereby the blades are simultaneously subjected to angular movement.

3. A propeller hub structure comprising a pair of castings adapted to be joined by ring nuts at the ends constituting the extremities of the hollow hub axis, split annuli disposed in the hollow axis at the respective-ends thereof and abutting against a one-direction thrust bearing disposed against shoulders in said hub, said annulus having grooves which are adapted to engage complementary shaped anchorage abutment of the propeller blade root, and clamping rings disposed in the endsof the hub and adapted to intimately engage and contact the annuli whereby to firmly anchor the blade roots in the hub.

4. A propeller hub structure comprising a split hub having a hollow axis and joined by ring nuts and studs, rotatable members disposed in said hollow axis and abutting against roller races in the direction of the propulsive thrust, said rotary members being adapted to clamp the blade roots and being provided with means for adjusting the blade roots and securely locking them in their adjusted position, a pitch coordinating bevel gear having gear-tooth engagement with said rotatable members, a coil spring normally bias- 2 ing said pitch coordinating gear in one direction,

and actuating means for subjecting said gear to rotary movement whereby the rotary members carrying the blade roots are subjected to angular movement to adjust the pitch of the propeller blade. t

' 5. A hub structure for variable pitch propellers comprising a plurality of split castings joined to constitute a front and rear section, the latter being provid i with a spline for engagement with the propeller shaft, split beveled annuli disposed in the hollow axis of the hub and having onedirection thrust roller bearings abutting the shoulders thereof, tapered locking sleeves for clamping said split annuli to intimately engage and secure the propeller blade roots, gear teeth provided on one half of the beveled faces of said annuli, a pitchcoordinating bevel gear having its teeth interacting with the teeth of said annuli in member.

the foremost position of blade setting, and wheating means adapted to actuate said bevel gears through said spring to subject the propeller blades to variable pitch setting.

6. A propeller hub structure for variable pitch propellers comprising a pair of castings joined to constitute a front and rear section, the latter being provided with a spline member forengaging the end of the propeller shaft, said hub being provided with a relatively large space in the front half for receiving pitch adjusting mechanism, a plurality of clamping members adapted for rotary movement in the hollow axis of said hub' and having-roller races in abutment with shoulders provided thereon, one of the races being clamped on said members to adapt it to rotate therewith, an

actuator for said rotary member in gear tooth engagement therewith, and a hydraulic unit operatively connected to said actuator to adapt said rotary members to angular movement for pitch adjustment, said hydraulic unit being removable to provide a large opening to render the interior of the hub accessible for the assembly of .the rear half to the propeller shaft, and for the assembly of the pitch coordinating mechanism therein.

7. A propeller hub structure for hollow blades comprising a pair of castings joined to constitute a unitary member, blade anchorage annuli in said I hub, and conduits clamped therein having their ends disposed in said annuli and terminating in a common end chamber.

8. A hub, structure for hollow blade propellers comprising a. plurality of castings, clamping means therefor, blade anchorage annuli for interlocking the blade roots with the hub, and motor exhaust conduits extending in said annuli and terminating in an end chamber, said conduits being secured in said hub by the hub clamping means.

9. A propeller hub as set forth in claim 8 in which the end chamber of the exhaust conduits is provided with gas impelling vanes.

10. A propeller hub as set forth in claim 8 in which a pair of exhaust conduits are joined at one end to form an annular chamber;

11. A hub structure for hollow metal propellers comprising an integral casting having a socket for receiving the propeller actuating engine shaft, an annular chamber surrounding said socket for receiving scavenged fumes from the propeller actuating engine, and a pair of conduits leading from said chamber and extending through said hub into the blade roots of said hollow propeller blades to conduct the scavenged fumes into the hollowness of the blade structure, said propeller o hub drive socket, annular chamber and conduit being integrally formed to-constitute a unitary WALTER S. HOOVER. 

